Fuel cells are well known in the prior art. A fuel cell differs from a battery in that it is a thermodynamically open system where the fuel source reactant is continuously supplied from an external source. Microbial fuel cells (MFC's) are also well known in the prior art. A MFC can use the metabolic process of microbes (such as bacteria, for example) from the surrounding environment to catalyze the conversion of chemical energy into electrical energy. More specifically, electrical charges can be generated and expelled during the metabolic process of bacteria, which converts organic matter in the soil or sediment, such as acetates, fatty acids, and aromatics, into by-products of carbon dioxide and positive hydrogen ions. Microbial fuel cells essentially take electrons from bacteria either directly or indirectly, and convert into electrical energy. Compared to traditional fuel cells, MFCs can be more flexible to operate, less expensive to construct, and can harvest energy directly from the environment, waste streams, and other ubiquitous sources of organic matter. MFCs have found applications in harvesting energy from sediments in rivers, lakes, and oceans, as well as from a range of waste streams such as municipal sewage treatment plants.
For an MFC to function effectively, the generated charges must effectively transfer from the bacteria to the anode of the MFC. Once this occurs, the resulting electrical current can travel across and through the anode to either serve as an electric energy source to instantaneously power load electronics, or to charge storage devices such as batteries, capacitors, super capacitors and similar components. Energy (electrical charges, or electrons) that is not dissipated in the load electronics can continue to flow to the cathode, to chemically react with oxygen and positive ions and thereby create thermal energy and chemical by-products. But in order for this to occur, the MFC anode must generally be operated under anerobic conditions while the MFC cathode must be operated under aerobic conditions. For benthic MFCs operating on the seafloor (BMFCs), this generally requires that the anode be buried beneath the sediment surface, while the cathode is suspended in the water above the sediment. Positioning these components is vital to the success of these BMFC systems, since the electrodes must each be placed in specific, isolated locations of the environment relative to the natural reduction-oxidation (redox) gradient.
Deployment of BMFCs by divers has traditionally been the primary mechanism for ensuring proper orientation and placement of the anode and cathode at the sediment ocean interface. Other methods that have been used can include sled deployment, placement by remotely operated vehicle, and in very shallow water, systems have been deployed by wading or divers.
Once seafloor systems, such as the self-burying system described here, have been deployed, their persistence (effective deployment life) is typically limited by the finite energy of an enclosed battery. If a BMFC were integrated into the self-burying system, it would be possible to “trickle charge” the system with energy harvested by the BMFC and thus significantly extend the life cycle of the self-burying device.
In view of the above, it is an object of the present invention to provide an MFC that is self-burying. Another object of the present invention to provide an MFC that is self-sustaining, in terms of generating its own operating power. Still another object of the present invention is to provide an MFC that provides an increased deployment life cycle of seafloor systems. Yet another object of self-burying MFC of the present invention can be to provide added anchoring strength for the MFC, to guard against and withstand fishing hazards, such as fishing nets and the like. Another object of the present invention to provide a MFC, which can be easily deployed, without the use of divers or additional equipment. Still another object of the present invention to provide a MFC, which can be manufactured and deployed in a cost-efficient manner.